Oregon’s old treasures

Old-growth forests are more complex than any other kind of forest, and they are home to a diversity of animals, insects, fungi, mosses and lichens. These older forests are a crucial piece of Oregon’s forest mosaic, and provide habitat for threatened species such as the northern spotted owl and the marbled murrelet.

Logging of old-growth forests virtually never occurs in Oregon. Today, an old-growth forest in Oregon is much more likely to be lost to wildfire than to timber harvest. What little is harvested is usually done to restore forest health or protect public safety.

About a third of the forests in Oregon, mainly federally managed, are designated as reserves and have essentially no timber harvest. This includes wilderness areas and parks where old-growth is protected as important wildlife habitat and for its value to outdoor recreation.

Classifying old-growth

Old-growth forest classification is more about forest structure and function than it is about tree age. Scientists classify forests as old-growth based on the following characteristics:

tree size

accumulations of large, dead woody material, both standing and fallen

the number of canopy layers

vertical and horizontal diversity in the canopy

species composition in the understory, including a variety of tree
and plant species

Active forest management can help protect old-growth

Protecting old-growth forests doesn’t always mean locking the gate and walking away. Protection often requires an active hand. Thinning can be used to reduce the competition for sunlight, water and nutrients among the remaining trees, allowing them to grow larger in a shorter period of time and creating ideal habitat for species such as the spotted owl.

On the east side of the Cascades, where there is less rainfall and frequent fires have been kept out of the ecosystem, active forest management such as thinning and clearing away dry brush is needed to help preserve old-growth forests and protect them from being destroyed in wildfires.